Så bra att jag tom klistrar in en kopia här (jag litar inte på att rapporten får ligga kvar i evighet, den kan bli bortplockad om vissa får som de vill..), Nu har vi i allafall en väl dokumenterad bil som bevisligen klarar 100% E85 trots att tillverkaren inte medger det.
Med utmärkta emissioner dessutom.
Kanske har produktutvecklingsavdelningen på Toyota tänkt längre än marknadsavdelningen
AET/MSU 489 - 35
04/21/2004
THE CREED PROJECT: 2003 Toyota Prius Hybrid
Conversion to Ethanol
Andy Tan, Ahmed Shebe, Dai Wakahoi, Kazumaza Hirasawa, George Luna
Automotive Engineering Technology, Minnesota State University
Dr. Paul Sullivan
Advisor
ABSTRACT
A 2003 Toyota Prius Hybrid-Electric vehicle was tested for operation on E-85
(85% ethanol/ 15% gasoline). Tests were done to determine if the vehicle could
be operated safely on E-85 without any alterations.
The vehicle was monitored, while slowly increasing the percentage of ethanol,
for conditions, which would indicate it would require system modification to adapt
the car to operate efficiently and reliably on E-85. Tests were also conducted to
compare operating on 89-pump gasoline against E-85. The fuel’s effects on
emission levels, fuel economy, power output, and drivability were found
INTRODUCTION
According to Toyota, the Toyota Prius was designed primarily to improve
emissions in urban driving and increase fuel economy. The Prius consists of a
parallel hybrid power train, called the Toyota Hybrid System (THS). This system
combines a 1.5 liter 4 cylinder gasoline engine, an electric motor, a generator,
and a Power Split Device, that also acts as a Continuously Variable
Transmission (CVT).
The Power Split Device is at the center of the Toyota Hybrid System. It is a
gearbox that is connected to the gasoline engine, the generator, the electric
motor, and the differential. This device makes it possible to operate the vehicle
using as a power source either the electric motor, or the gasoline engine, or both
power plants combined. The gasoline engine can also operate independently of
the vehicle speed, allowing it to charge the batteries for the electric motor –
eliminating the need for external power source for charging the batteries.
When the batteries for the electric motor are fully charged and the engine
temperature has reached the normal operating level, the Prius will use only the
electric motor to get the vehicle going from start to approximately 15 mph before
operating on the gasoline engine. Switching between the two power plants or
operating on both is achieved seamlessly – again due to the Power Split Device
that allows the generator to start the gasoline engine at any time without the
need for a starter. Skid-control also utilizes the Power Split Device in conjunction
with the electronic throttle of the gasoline engine.
In the center of the Prius dashboard is a multi-informational display screen
that indicates energy consumption status, power-flow, trip information and
consumption, audio system settings, navigation, and more.
The fuel tank in the Prius has an 11.9-gallon capacity, which Toyota
estimates will provide a range of 500 miles between refills.
TESTING
Most tests were conducted at Minnesota State University’s facilities in
Mankato (MSU, M). Emission and highway fuel economy testing were conducted
using the school’s inertia dynamometer, constant sampling system and analytical
exhaust gas analyzers as per U.S. EPA regulations. Drivability and real world
mileage were determined on the road.
DYNAMOMETER TEST
The L.A.4 FTP 78 driver traces were used to determine exhaust emission
characteristics, and EPA HWC.TRC was used to determine highway fuel
economy.
Power output testing was also conducted at MSU, M using a Mustang 2000
Dynamometer.
Fuel was tested for ethanol concentration levels before and after every test.
No tests were conducted to ascertain what long term effects high concentrations
of ethanol would produce on the components that are exposed to it.
ROAD TEST
Road tests were conducted on a route depicting varying load conditions and
drive-cycles representative of urban, highway, and short trips. During the road
tests, the vehicle was monitored for drivability, and the fuel control system’s
adaptive capabilities.
While all the tests were conducted with as much control as possible to reduce
variability, the road tests had to be repeated a greater amount of times. One
driver was selected for all the tests to provide greater consistency and
repeatability in the results.
During tests that required the use of a dynamometer, the skid-control had to
be disabled to allow the front wheels to exceed 19 mph, while the rear wheels
remained fixed. This was done by activating the Inspection Mode, which only
utilizes the gasoline engine for driving the front wheels. Since this research was
concerned with the comparison of fuels in the engine, the Inspection Mode also
served to eliminate any effects from the electric motor. Evidence of this can be
seen in the lower fuel economy results from the FTP HWC.TRC tests for both
gasoline and ethanol, compared to the results from the on-board computer that
were attained from road tests. The Inspection Mode was not used during the
road tests; Toyota strongly advises against it due to safety concerns.
RESULTS
While the results from the exhaust emission tests showed a decrease in all
levels of emissions, the levels of Hydrocarbons (HC) and Nitrogen Oxides (NOx)
were significantly reduced. The reason for only a small reduction in Carbon
Monoxide emissions was primarily caused by a high count during the first phase
of the L.A.4 FTP 78 trace. The first phase of this trace begins with a cold start.
One of the differences between the properties of ethanol and gasoline that plays
a crucial role; in cold starting and operating conditions, is their respective Reid
Vapor Pressure.
Reid Vapor Pressure a measure of a liquid’s ability to evaporate. It is
measured at 100º F, and the higher pressure indicates easier evaporation.
Gasoline is rated between 8 and 15psi, while ethanol is rated at 2.3psi.
A rich Air/Fuel ratio, high equivalence ratio, will produce higher levels of CO
emissions, while leaner Air/Fuel ratios will produce the minimum CO emissions.
During cold start and driving, the vehicles fuel management system provides a
richer (lower) air/fuel ratio required for cold starts and then leans (increases) the
air/fuel ratio gradually as the coolant temperature rises. It was seen that by the
second phase of the trace, the CO levels produced by the use of ethanol were
48.8% less than those produced by gasoline. In the third phase of the trace the
levels of CO were 39.2% less. Yet, the overall results only produced a reduction
of 5.5%. During the first phase, ethanol produced higher levels of CO over
gasoline with a 53.7% increase.
Similar results were obtained for Hydrocarbons emissions, except that in the
second and third phases of the trace, ethanol showed greater reductions than
gasoline.
Drivability during the road tests also highlighted the difference in cold driving
performance between the two fuels. When the engine was powered using
ethanol it felt sluggish and the idle quality was rougher. After a time of between 9
to 15 minutes, the ethanol performance improved and there was no noticeable
difference in drivability between the two fuels.
While using E-85, the check engine light came on. Upon inspection this
produced a code indicating a lean condition was detected. During this testing, it
was noted that the check engine light for the lean code would come on between
140-160 miles after clearing the code. The oxygen sensor output and the shortterm
fuel trim all indicated that the Air/Fuel ratio is stoichiometric, and that the
fuel control module was maintaining the correct amount of fuel required. What is
setting off the check engine light is that the system monitors the change in the
base fuel map, which is indicated by the long-term fuel trim. If this change is
outside of the set boundaries for an extended period of time, then a code is set to
indicate that the fuel system is making greater adjustments to the fuel quantity to
maintain the correct air/fuel mixture than is necessary under normal
circumstances. The use of ethanol caused the fuel system to adapt the long-term
fuel trim by an increase of 32.81%. ! This supports the lower average fuel
economy of ethanol in the results. See figure 4. An added advantage of using E-
85 showed gains in power output, as shown on table 1. Although ethanol has a
lower energy density than gasoline, due to its lower air/fuel ratio, and effectively
cooling the intake charge, it allows more fuel to be introduced to the combustion
chamber thereby providing the power gains seen.
Since E-85 tests were not done at ambient temperature of 25ºF or less, it is
not possible to comment on starting abilities in such conditions. While at 25ºF the
vehicle started without difficulty.
Table 1: Maximum power and torque comparison
Fuel Type Maximum Power Maximum Torque
Gasoline 64bhp @4500rpm 80lb-ft @4200rpm
E-85 77bhp @4700rpm 106lb-ft @4250rpm
Results showed the benefits of using E-85 in the reduction of emission
pollutants compared to gasoline, but fuel economy dropped. These results were
obtained without any alterations to the stock vehicle for optimizing it to run on E-
85. See figure 1 & 2
Figure 1: Emission comparison on federal, stock & E-85
Emission Comparison: Federal, Stock,
and E-85
0
1
2
3
4
THC CO NOX
Emission Types
Emission Weight
(grams/mile)
Federal
Stock
E-85
Figure 2: Emission comparison focusing on THC & NOx
Emission Comparison: Federal, Stock,
and E-85
0
0.1
0.2
0.3
0.4
0.5
THC NOX
Emission Types
Emission Weight
(grams/mile)
Federal
Stock
E-85
Figure 3: Horsepower comparison output at wheel
Figure 4: Highway fuel economy comparison
CONCLUSIONS
This research showed that it is possible to operate the Toyota Prius Hybrid
using an E-85 fuel blend, weather conditions permitting, to provide further
reductions in exhaust gas emissions. There are some issues of concern.
Further research must be done to assess the impact of E-85 on the
components of the fuel system, such as the fuel lines, injectors, fuel pump,
catalytic converter, oxygen sensor, and the fuel tank. The fuel map and control
program needs to be developed to deal with the increased fuel requirement of E-
85 compared to gasoline; otherwise a check engine light will be activated. Since
cold-running operations provided the least reductions, in some case increases in
exhaust emissions, short trips from cold starts may actually increase the levels of
emissions. Developments must be made to improve cold starting performance. It
could be done through pre-heating of the fuel, and/or pre-heating of the catalytic
converter, or increasing the Reid Vapor Pressure of E-85.
As a research project, it was felt that all those involved have benefited
through the knowledge acquired in dealing with the involvements of a team
research project. The students gained the experiences of dealing with technical,
automotive, management, communication, and financial aspects of a research
project involving teamwork. In this respect, this was a successful project.
ACKNOWLEDGEMENTS
Aiken Roger– Former executive, CREED
Sullivan Paul– Assistant Professor, AMET
Jones Bruce – Professor, AMET
URC – MSU, Mankato
REFERENCES
Toyota USA,
www.toyota.com
Personal interview: Dr. Jones (AMET Professor)
“Internal Combustion Engines and Air Pollution,” Obert, E.F., 3rd Edition, Intext
Education Publishers, 1973.
Petroleum Products Surveys, Motor Gasoline, Summer 1986, Winter 1986/1987,
National Institute for Petroleum and Energy Research
API Technical Data Book – Petroleum Refining, Volume I, Chapter I. Revised
Chapter 1 to First, Second, Third and Fourth Editions, 1988
CONTACT
AMET Department, TE 205
Dr. Sullivan Paul
MSU, Mankato
Mankato, MN 56001
DEFINITIONS / ACRONYMS/ABBREVIATIONS
AMET – Automotive and Manufacturing Engineering Technology
API – American Petroleum Institute
CO – Carbon Monoxide
CREED - Communities for Responsible Energy and Environmental
Demonstration
E-85 – 85% of ethanol and 15% of gasoline
EPA – Environmental Protection Agency
FTP – Federal Test Procedure
Fuel trim – The correction factor to command fuel injectors. Based on learned
values between maps in the ECU, and signals to the fuel injectors to compensate
for required fuel.
HP – Horsepower
HWC .TRC – Highway trace for fuel economy
LA4 – A name of drive cycles used in superflow emission dynamometer
MSU,M – Minnesota State University, Mankato
NOx – Oxides of Nitrogen
PSI – Pound per square inch
Reid Vapor Pressure – Vapor Pressure at 100ºF
Stoichiometric – The correct amount of fuel and air mixture for complete
combustion
THC – Total Hydrocarbon
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